General Application and Selection of the Flex-Hone® Tool
is only a general guide. For specific applications and recommendations
please contact us
This is only a general guide. For specific applications and recommendations
please contact us
How To Use a Flex-Hone Tool
|How To Use a Flex-Hone Tool|
The Flex-Hone Tool is a resilient, flexible honing tool used to improve the internal surface finish of a bore or cylinder. It is comprised of abrasive globules laminated onto the ends of flexible nylon filaments. It's unique construction allows the tool to be self-aligning, self-centering and self-compensating for wear. The tool provides the benefit of removing loose, torn and folded metal and creating a substantially flat or plateau surface. An additional important application for the Flex-Hone Tool is burr removal from cross-drilled holes.
The Flex-Hone Tool is manufactured in 8 different abrasive types and 11 different grit selections in a wide selection of sizes to work on a broad variety of base materials and surface finish requirements. The tool is produced in diameters from 4mm to 36".
Tool diameter is determined by the nominal bore size in which the tool is to operate. The Flex-Hone tool is always produced and used in an oversize condition. The degree of oversize creates a soft cutting action. For example, a 1" Flex-Hone size is ordered if a 1" bore is to be finished and the tool is provided oversized. If the bore size is between standard Flex-Hone sizes, the next larger standard Flex-Hone should be selected. For instance, if the nominal bore is 1.093", then the 1-1/8" Flex-Hone is ordered.
Abrasive selection is largely dependent on the base material
being finished and whether the application is for surface finishing
Silicon carbide is by far the most popular abrasive type. It is used to finish mild steel, stainless steel and cast iron.
Aluminum Oxide is the next most popular abrasive and it is used to finish non ferrous materials like aluminum, brass, bronze, softer metals and plated cylinders.
Zirconia Alumina (Z-Grain) has very similar cutting properties to silicon carbide and can generally offer longer tool life. It is available in two grades: #1525 (25% Zirconia, 75% Alumina) and #1549 (40% Zirconia and 60% alumina). It is used to finish low carbon to medium carbon steels, stainless steel and cast iron.
Boron Carbide is used to finish medium to high carbon steels and heat-treated steels to 50 Rc. It is also useful in titanium, Inconel and Monel. Tungsten Carbide is used for the high carbon steel alloys and more exotic space age alloys.
Levigated Alumina is a super fine abrasive used for a final polish on many materials. This abrasive should be used where Ra requirements are very low.
CBN and Diamond are experimental and are not commercially available at this time.
The amount of work to be performed and the degree of surface finish improvement required govern grit selection. Coarse finishes may require progressively finer Flex-Hones to meet final surface finish requirements. In very general terms, final finish will be in the following ranges. This chart is intended to offer a starting point in selecting a grit but the final selection must be verified by actual trial.
Grit Finish Range
800-LA Ra 3-10 (.05 - .2 Micrometer)
600 Ra 8-12 (.2 - .3 Micrometer)
400 Ra 10-20 (.3 - .6 Micrometer)
320 Ra 18-30 (.5 - .7 Micrometer)
240 Ra 24-32 (.6 - .8 Micrometer)
180 Ra 30-40 (.7 - . 1 Micrometer)
120 Ra 35-50 (.9 -1.4 Micrometer)
80 Ra 45-64 (1.2 - 1.6 Micrometer)
60 Ra 60-80 (1.5 - 2 Micrometer)
40 Ra 70-125 (1.7 to 3.2 Micrometers)
20 Ra 125-250 (3.2 to 6.3 Micrometers)
The Flex-Hone tool is a low RPM tool. Specific RPM is dependent on the diameter of the tool and the application. General speed ranges are given but, again, machine trials are required to verify the parameters.
Hone Dia. RPM
19" to 36" 60-120 RPM
12" to 18" 80 to 350 RPM
8" to 12" 300 to 500 RPM
4" to 8" 400 to 600 RPM
2" to 4" 600 to 800 RPM
½" to 2" 700 to 900 RPM
4mm to ½" 800-1200 RPM
Stroke rate is a function of Flex-Hone diameter, stroke length and cross hatch angle specification, if any. High crosshatch angles require faster stroke rates. The larger diameter tools might feed as slow as10-12 IPM while the smaller diameter tools with high cross hatch angles might require feed as high as 250 IPM.
The hone can be made to rotate in both directions. Often this is preferable to do on each work piece (i.e. 5 strokes clockwise, 5 strokes counterclockwise)
The Flex-Hone tool always requires the use of a lubricant or honing oil. Finer surface requirements dictate better quality honing fluids be used. Many fluids may be used general applications: water soluble oils, mineral oils, motor oils and cutting and tapping fluids are adequate to keep the tool from loading and to insure exposure of fresh cutting particles. Solvents should be avoided, as they tend to degrade the adhesive bond in the tool.
The Flex-Hone can be used until there is virtually no abrasive
left on the filaments. Cutting curves can be plotted to show when
to replace the tool. Many users will increase the number of strokes
used at a point in the tool wear to compensate. Tool life can
be increased if the tool is reversed every 4th or 5th part. It
is also effective to reverse the tool a portion
of the cycle if cross drilled holes are present.